Add NonEmptySet (#2143)

* Add NonEmptySet * Make NonEmptySet a semilattice and add extra test * Fix doctest * Remove AnyVal and rename to toSortedSet * Add more docs * Add concatMap * Newtype encoding * Move newtype to its own file * Address feedback * Remove Order constraint for fromSet constructor * Remove Context bounds * Make newtype private
typelevel · Mar 14, 2018 · 3503cea · 3503cea
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diff --git a/core/src/main/scala/cats/data/Newtype.scala b/core/src/main/scala/cats/data/Newtype.scala
@@ -0,0 +1,12 @@
+package cats
+package data
+
+/**
+  * Helper trait for `newtype`s. These allow you to create a zero-allocation wrapper around a specific type.
+  * Similar to `AnyVal` value classes, but never have any runtime overhead.
+  */
+private[data] trait Newtype { self =>
+  private[data] type Base
+  private[data] trait Tag extends Any
+  type Type[A] <: Base with Tag
+}